5.2 Blundell Rules Limited, UK

The family firm of Blundell Brothers Limited, formed in 1852 in Luton, England, began to make slide rules following World War II, when the German-made slide rules that had been prolific in the U.K. were by then in very short supply. By 1948 the family formed the separate company Blundell Rules Limited and eventually moved to a new factory location in Weymouth in 1956. By 1963 BRL had become a quality manufacturer of slide rules and other instruments. In 1964 the company purchased the assets of W.H. Harling Limited, bringing high-quality drawing instruments into their repertoire. While the company’s primary production of slide rules ended in the 1970s as electronic calculators took over, Blundell Harling still exists today as “… UK’s premier manufacturer of drawing boards, architect supplies, draughting equipment and graphics accessories.”11

For a nice overview of Bludell Rules, see the article by Peter Soole in the 1998 Journal of the Oughtred Society, vol.7 No. 1, p.17.

Total number of Blundell slide rules in the collection: 4. \(~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\)

Model Year Type Mat L0 Case Note
AL6 1949-1958 L pl 10.0 yes Pat No 644944; 3-hairline cursor; owner M. Levitt; original hinged box with clasps
Radiac No. 1 1952-1956 C pl 2.0 yes radiation exposure calculator; log log scales; reversible land/sea discs; instructions on back
Pilot Balloon Slide Rule Mark IV-A 1957-1964 L pl 7.5 box Used by the U.K. military/meteorologists to compute wind speed at various altitudes using data from sightings of “weather” balloons from ground-based telescopes; special thanks to Laurie,Peter(!),Stephen,Olivia,Arden for getting this to me from Australia
506 Academy Duplex 1970-1980 L pl 10.0 yes Vector slide rule; single hairline on front, 4 on back; yellow-tinted cursor on C/D, A/B, and S/D; Pat. No. 6225/67; case is stiff, not good shape


  1. Visit their web site.↩︎